Article View: comp.arch
Article #21159Need information about 386 performance
From: Paul Fronberg
Date: Wed, 10 May 1989 16:34
Date: Wed, 10 May 1989 16:34
22 lines
1672 bytes
1672 bytes
I am doing analysis of the i386 for use as in a controller and am having problems relating calculated timings with measured timings. Does anyone know about any documentation, ap-notes, or such that might be available from Intel that describes the inner workings of the i386, especially how the various phases of the pipeline interacts. The measured time and calculated time are very different for several test code fragments (The measurements were on a 386 Unix box with 0 wait state memory, 32 bit bus). I suspect I am seeing collisions between instruction prefetch and instruction memory accesses. Things seem to be very complicated when the MMU is activated and the memory is not 0 wait state and I am sure that the pipeline timing diagrams I am generating are anywhere correct. The hardware and software reference manuals are very skimpy when it comes to information of this type. The timing information given in the programmers reference manual gives only execution cycles, assuming that the instruction has already been prefetched and decoded. There seems no information concerning the effects of MMU, addressing, etc. Any help or information would be most appreciated. Paul Fronberg
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!decwrl!nsc!unixprt!paf From: paf@unixprt.UUCP (Paul Fronberg) Newsgroups: comp.arch,comp.sys.intel Subject: Need information about 386 performance Keywords: i386, pipelining, clock cycles, performance Message-ID: <390@unixprt.UUCP> Date: 10 May 89 16:34:46 GMT Followup-To: poster Organization: uni-xperts, Inc. - Unix System and Networking Consultants Lines: 22